In order to miniaturize piezoelectric devices, e.g., piezoelectric thin film filters (BAW filters) and surface acoustic wave filters (SAW filters), a CSP (chip size package), in which an element chip and a cover are sealed by a bonding layer formed along outer edges of their respective main surfaces, has been proposed previously (refer to, for example, Patent Documents 1 and 2).    Patent Document 1: Japanese Unexamined Patent Application Publication No. 2004-17171    Patent Document 2: Japanese Unexamined Patent Application Publication No. 2001-94390
In the configuration disclosed in Patent Document 1, a wiring connecting between an excitation electrode and an input and output external electrode disposed on the circumference surface is formed on a piezoelectric filter chip main surface. Since this wiring intersects with a bonding layer which bonds the filter chip to the cover, the bonding layer must have an insulating property.
In the configuration disclosed in Patent Document 2, a sealing component is formed from an electroconductive bonding material along outer edges of a base substrate and a surface acoustic element so as to bond and seal. This sealing component is not grounded.
Each of these configurations has poor shielding properties.
The heat generated from the filter is transferred through the wiring and is released from an external electrode to a mounting substrate. The degree of heat release varies depending on the arrangement of the external electrode of the piezoelectric filter.
In the configuration in Patent Document 1, the wiring from the excitation electrode (heat generation portion) reaches the end of the piezoelectric filter through a portion in which the piezoelectric element and the cover are bonded together, and is connected to the mounting substrate through the external electrode formed on the side surface of the cover. Therefore, the route becomes relatively long, and the heat releasing property is poor.
In the configuration in Patent Document 2, one end of a through hole penetrating the cover is connected to a pad, which is connected to the excitation electrode, and the other end is connected to the external electrode. Therefore, the distance between the heat generation portion and the mounting substrate is short. However, since the arrangement of the external electrode is not taken into consideration, the heat releasing property to the mounting substrate is not always good.